Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations already declare readOnlyHint=true, and the description reinforces this with 'read-only'. It adds valuable behavioral context beyond annotations: the 1-credit cost, the live nature of the data, the platform constraint, and the account requirement. Slight deduction because the phrase 'call it to get a signup link' is a bit ambiguous about which tool or endpoint to call.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is longer than average, but each sentence earns its place: mode of operation, platform limitation, credits, alternatives, and account requirement. It is front-loaded with the core action and usage pattern. Minor verbosity in the alternatives section keeps it from a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only tool with no output schema, the description adequately covers mode selection, platform scope, credits, auth prerequisite, and sibling routing. It names the relevant include option and what the tool returns ('metadata' and 'rules'). A fully complete description might clarify what happens when both query and channel are omitted, but the required-platform schema and the explicit 'pass query...or channel' framing make this a minor gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents query, channel, include, and platform. The description adds useful usage framing (search vs exact channel, include:['rules']) but does not materially expand on the parameter semantics already present in the schema. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states a specific verb ('Discover or inspect') and resource ('channels (Reddit subreddits)') with a qualifier ('LIVE'). It also distinguishes this tool from sibling catalog and research tools by naming exactly what this tool does and what it does not do, so an agent can differentiate it without opening schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives explicit when-to-use guidance: use this for live metadata/rules or subreddits outside the catalog, use catalog_search_subreddits/catalog_get_subreddit for cached data, and use research_run/research_get for ranked reports. It also explains the Reddit-only limitation and tells which parameters to pass for which mode ('Pass query to search, or an exact channel').

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.